樟树幼树光合特性及其对CO_2浓度和温度升高的响应

Photosynthetic Characteristics of Cinnamomum camphoraand Its Response to Elevation of CO_2 and Temperature

用Li COR 6 4 0 0便携式光合作用测定系统对亚热带常绿阔叶树种樟树幼树的光合特性及其对CO2 升高的响应进行了研究。结果表明 :樟树叶片光合速率日变化呈双峰曲线 ,最高峰出现在 10 :0 0 ,次高峰出现在 14 :0 0 ,午间有明显的“午休”现象 ,气孔因素是导致午休的主要原因。中午光照强度大 ,叶片与空气之间的水汽压差达到最大值 ,相对湿度、气孔导度、胞间CO2 浓度达到最小值 ,诱导叶片光合午休。正常大气条件下 ,樟树叶片光饱和点为 12 5 0 μmol·m- 2 s- 1 ,光补偿点 4 0 6 μmol·m- 2 s- 1 ,在 10 0 0 μmol·m- 2 s- 1 光强下CO2 饱和点为 12 0 0 μmol·mol- 1 ,CO2 补偿点为 5 0 μmol·mol- 1 。水分利用效率、气孔导度、蒸腾速率在不同的CO2 浓度梯度下 ,随着光强的增加而增加。在 2 4～ 35℃时 ,随着光合有效辐射的增加 ,温度升高导致樟树光合速率降低。

The photosynthetic characteristics of Cinnamomum camphora and its response to CO 2 enrichment in subtropical evergreen broadleaf forest area were investigated using Li_COR 6400 portable photosynthesis system. The results showed that the diurnal net photosynthetic rate of C.camphora in sunny day varied with double peak curves. The peaks occurred at 10:00 and 14:00 respectively. There was a significant midday depression. Stomatal factors, such as the stomatal conductance, were the main causes of the depression. At midday, light intensity was the largest, vapor pressure deficit between leaves and air reached maximum, but air relative humidity, stomatal conductance and intercellular CO 2 concentration were minimum, and hence photosynthetic middy depression occurred. The light compensation point and light saturation point of leaves at the ambient CO 2 concentration were 40 6 μmol·m -2 s -1 and 1 250 μmol·m -2 s -1 ,respectively. When light intensity reached 1 000 μmol·m -2 s -1 and ambient CO 2 concentration, its CO 2 compensation point and CO 2 saturation point were 50 μmol·mol -1 and 1 200 μmol·mol -1 ,respectively. With the increases of light intensity, water use efficiency, sotmatal conductance and transpiration rate were improved at different CO 2 concentration. And in 24～35℃,the net photosynthetic rate showed a decreasing trend with the temperature and photosynthetic active radiation increasing.